The present invention relates to the treatment or repair of vasculature and more particularly, to delivering a graft device within a blood vessel to address vascular disease.
In recent years, there have been developments in the treatment or repair of the vasculature of humans or other living animals. These developments have been applied to various areas of vasculature to treat a number of conditions such as vessel weakening or narrowing due to disease. The methods developed have involved minimizing the invasive nature of repair so that patient morbidity and mortality can be reduced. The period of recovery has also been reduced with such advances.
Some people are prone to degeneration and dilatation of the aorta, leading to rupture and death from bleeding. A recently-developed method of arterial reconstruction involves the attachment of a tubular conduit (graft) to the non-dilated arteries above and below the degenerated segment using stents; hence the name “stent-graft” for the prosthesis. The lumen of the arterial tree is used as a conduit to the aorta; hence the name “endovascular aneurysm repair” for the procedure.
The procedure is relatively simple when the degenerated segment is without significant branches. The stent-graft needs only one lumen with an orifice at each end. But the procedure is much more complicated when the degenerated segment of the aorta contains branches, because the stent-graft also needs to branch and these branches need to be placed along multiple lines of insertion. The most common, and simplest, example is reconstruction of the aortic bifurcation. This technical hurdle was crossed relatively early. Yet there has been no significant progress in the intervening years towards reconstruction of areas with more branches, such as the suprarenal aorta, the aortic arch, or other complex vasculature near the kidneys or involving the hypogastric, iliac or femoral arteries. The main problem is that the branches are of variable size, variable orientation, and variable position. It is very difficult to create a graft that will mimic the native anatomy, and very difficult to place such a graft in exactly the right orientation and right position without causing ischemia of the vital organs that are fed by the aortic branches. This is especially true of the aortic arch, which has branches to the brain.
The aortic arch, for example, is affected by two degenerative processes, dissection and aneurysmal dilatation, that hitherto have been treated by open surgical reconstruction. The open surgical operation relies upon cardiopulmonary bypass, with or without hypothermic circulatory arrest. The associated mortality, morbidity, debility, pain and expense are all high.
Endovascular methods of reconstruction must deal with certain challenging anatomic features. For example, all three arteries that take origin from the aortic arch supply blood to the brain. Flow through these arteries cannot be interrupted for more than five minutes without risking irreversible neurologic damage. Moreover, the distribution of the arteries in any one patient, and the arch arteries, in particular, is highly variable. It is, therefore, not feasible to mimic this arrangement in every patient without very sophisticated reconstruction. Even if the graft matched the patient's anatomy precisely, it would still be difficult to match the orientation and position of the branches of the graft to the branches of the native vasculature. Additionally, the arch arteries, for example, usually arise from the ascending portion of the arch at acute angles to the downstream aorta. Trans-femoral access to the arch arteries necessitates a sharp change of direction where these arteries arise from the aorta.
However, certain anatomic features lend themselves to endovascular repair. The aorta and in particular, the ascending aorta is long, straight and without significant branches. Further, the aorta is wide and consequently, there would be room for a main or primary graft conduit to lie alongside its branches. Also, it is relatively easy to gain access to the femoral and iliac arteries.
Thoracic aneurysms typically occur in frail elderly patients, who tolerate thoracotomy and aortic cross-clamping poorly. Hence, there are high morbidity and mortality rates of open surgical repair for such patients. Endovascular exclusion can be an appealing alternative, particularly when the aneurysm involves the aortic arch and open repair would require reconstruction of the brachiocephalic circulation under hypothermic circulatory arrest. However, to be successful, the endovascular technique must deal with a number of challenging anatomic obstacles specific to this segment of the aorta. One is the tortuosity of the aortic arch. Another is maintaining uninterrupted blood flow to the arms and the head, while excluding the rest of the aortic arch from the circulation.
Endovascular techniques offer two distinct advantages over conventional open operative technique in the repair of aortic arch aneurysm or dissection. First, the endovascular graft is inserted through remote, easily accessible arteries outside the body cavity, whereas the open operation often requires a combination of median sternotomy and lateral thoracotomy for insertion. Second, the endovascular graft can be deployed without interrupting blood flow, while open repair usually requires aortic cross-clamp and hypothermic circulatory arrest.
Since the challenge in endovascular repair, as in surgical repair, is to maintain blood flow to the brain and upper extremities, various approaches have been contemplated. One option is to provide the stent-graft with side branches to the innominate, left carotid and left subclavian arteries. Another is to perform a surgical bypass from either the proximal ascending aorta or from the femoral arteries. A third alternative that combines aspects of the other techniques can be desirable for certain high risk patients. That is, a technique that provides blood flow to the innominate artery through a branch of the modular stent-graft, and blood flow to the left carotid and subclavian through extra-anatomic surgical bypass.
Accordingly, what is needed and heretofore unavailable is a system and method for treating or repairing complex vasculature while minimizing risk and the recovery time of the patient. The present invention meets these and other needs.